Lecture 13: Life History Tradeoffs Flashcards
Not all individuals contribute in the same way to
population dynamics
An organism’s life history is
a record of events relating to its growth, development, reproduction and survival
Life history characteristics include:
Survival and mortality rates
Age and size at sexual maturity
Amount and timing of reproduction
Life history strategy of a species
The overall pattern in an average timing and nature of life history events
Shaped by how the organism allocates energy and resources between growth, reproduction, and survival
Associated tradeoffs with allocation patterns
Within a species, individual strategies may differ because of
genetic variation, environmental conditions, or both, which can affect the species success
Natural selection favors individuals
whose life history traits result in their having a better chance of surviving and reproducing (fitness)
All organisms face ___ and _____
constraints
ecological trade offs
Complex life cycles
At least two stages with different body forms that live in different habitats and eat different foods
Metamorphosis
Ex of complex life cycle
Abrupt transition between larval and juvenile stages
Complex life cycles found in
Common in insects, marine invertebrates, amphibians and some fishes
Many plants, algae, and protists also have complex life cycles
Trade offs along life history are ___
ubiquitous
investments: energy, resources, time
Life history trade offs involve
allocate energy to current reproduction OR grow bigger first (risking death in the meantime) and then reproduce
few large offspring or many small offspring
Allocating resources to reproduction from trade off can
decrease an individual’s growth rate, survival rate, or potential for future reproduction
Ricklefs observed trade off between
annual fecundity and annual survivorship in bird species
different morphologies and behaviors are
adaptive at different life cycle stages
___________ over the course of the life cycle are responsible for distinctive patterns in the life histories of organisms
Differences in selection pressures
Organisms have various mechanisms to protect
small life stages
Ex. Parental investment
Dormancy
State of suspended growth and development in which an organism can survive unfavorable conditions
Ex. small seeds, spores, eggs, and embryos are best suited to dormancy as less metabolic energy needed to stay alive
some larger animals can enter dormancy
_______ is common in complex life cycles
functional specialization of stages
Ex. of functional specialized of stages
In many insects the larval stage is specialized for feeding and growth; the adult is specialized for dispersal and reproduction
Luna Moths
Extreme example of functional specialization of stages:
Adults only have vestigial mouthparts and no digestive system
Eye spots to reduce predation
Wing tails create false target for bats to attack and moth breaks off tail (anti predator control)
Are there general patterns/categorizing species in the tradeoffs that organisms make in life history strategies?
Grime’s CSR triangle
r vs. K selected species
Grime’s triangle
Makes general categories of life history syndromes based on the environment
Stress vs. disturbance
How is Grime’s Triangle Organized?
Increasing disturbance from top to bottom
Increasing stress from right to left
Increasing competition from bottom to top
Stress-tolerant plants
Bottom left in Grime’s Triangle
Adapted to high stress, low disturbance habitats
Ex. Ivies, cacti
Ruderal plants
Bottom right in Grime’s Triangle
Adapted to high disturbance, low stress habitats
Ex. dandelions, lawns in front of house
Competitive plants
Top of Grime’s Triangle
adapted to low stress, low disturbance habitats
Ex. birch trees
Tend too be competitive
What does Grime’s Triangle not include?
plants adapted to high stress, high disturbance
To account for high stress high disturbance use different model CSR triangle of Grime
Stress= Habitat productivity
Disturbance= habitat duration
Original triangle with stress tolerators, competitors, and rooters is only half the space = tenable triangle (places plant can live)
High stress, High disturbance (Low habitat productivity, low habitat duration) represented in untenable triangle (plants do not live)
Categorize species by life history characteristics through:
fast to slow life history
Categorizes of syndrome for fast to slow life history
r-selected
K-selected
Fast r-selected
Species that do not do well under high resource conditions, immediately after disturbance
Slow K-selected
Species that are competitive and do well when resources are limited
Timing of ________ can be of critical importance
seasonal life history activities
Ex. importance of timing of seasonal life history
A bird that migrates north too early in spring may starve if no food is available
Long term data show that many species initiate spring activities earlier, apparently in response to climate change
Shifts in timing of seasonal don’t …
always keep pace with climate change
Ex. of how shifts in timing do not keep pace with climate change
Snowshoe have fur changes to white in winter, but the timing has not changed, even though snowfall begins later in the year
As shifts in timing do not keep pace with climate change, what can be result
Camouflage mismatch and increased mortality from predators
